The production of coke from petroleum residues is the last in the line of processes operating on a specific fraction by the petroleum refining industry, in that after all the processes of distillation, cracking, reforming, hydrogenation and the other more thermodynamically gentle and chemically precise processes, there remains only a high temperature reaction which is essentially a destructive distillation. The final residue from destructive distillations, no matter what the starting material, is almost always eventually a coke, a solid carbonaceous residue, usually amorphous, containing a complex mixture of a large number of high molecular weight residual compounds. Normally from 75 to 95% of the residue is in the form of a carbonaceous structure which is essentially a polymeric hydrocarbon with irregular aromatic and aliphatic groups, linked by aliphatic chains of inhomogeneous types.
There are several types of raw petroleum coke, including fluid, shot, regular or sponge, and needle coke. Regular grades may be used for fuel or calcined to remove the low molecular weight volatile matter. The largest volume single use of calcined regular delayed coke is in the manufacture of anodes for Hall cell production of aluminum.
Other uses of raw petroleum coke are disclosed in U.S. Pat. No. 2,603,592 by H. W. Nelson, a solution of coke in solvent useful as a binder and asphalt substitute, and U.S. Pat. No. 3,382,084, by Folkins, extraction of coke with basic nitrogenous organic solvents with a mixture of the extract and petroleum pitch used as a binder.
A large number of processes have been used to produce binder pitches from various petroleum residues, of which U.S. Pat. No. 3,318,801 to Alexander, Cl. 208-40, and Canada Pat. No. 811,042 to Mobil Oil, Apr. 22, 1969, are examples. Alexander discloses a binder somewhat similar in composition to the binder produced by the present process.